Recent content by ConcreteDrBill

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    Cement stains on Buff riven slabs

    A stiff brushing follwed by the application of a brickwork cleaner might help (try it out on a small area first).
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    sand and cement question

    Hmmmmmmmmmmmmmm!!!
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    sand and cement question

    Cement setting is a chemical reaction so it slows down at low temperatures. Whilst cement will set at 2C it will not gain much strength and will be very susceptible to frost attack (the water in the mortar freezes and expands, in a weak mortar this leads to cracking). You will need to protect...
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    what screed mix for underfloor heating

    1:4 cement:sand is OK for a screed under rigid floors like stone tiling
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    Quantity of water in screed

    You want enough water so that the screed material can be formed into a ball in your hands without crumbling or letting water out
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    Concrete Footings - Is there a problem ?

    The shelf life of cement is definitely related to mimimising the risk of allergic reactions (i.e the effective life of the reducing agent that converts soluble chromium (allergen) into insoluble chromium (safe). As Ronny Raygun says, if the cement in the bag has not gone hard or lumpy it...
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    Repointing with snowcrete?

    If you are trying to match the colour of the old pointing, remember that mortar always dries lighter than it looks in the mixer. The colour of the sand will affect the colour of the mortar. Depends on how close you want the match to be. 1 cement : 5-6 sand (vol) is a good general purpose mix
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    Concrete

    Mastercrete Oiginal is simply a cement (no sand or ballast)so you could also get 4 bags of Mastercrete and 18 bags of Ballast
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    Which type of mortar for pointing stone?

    You need Natural Hydraulic Lime (NHL) not Hydrated Lime (yes the are different) The Lafarge mortar contains cement as well as 'hydrated'lime, its good for general purpose pointing but not for weaker bricks or stone
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    crumbly concrete under floor

    Sulfate attack (if thats what it is) wont 'spread' to your neighbours property. If the construction of the neighbours house is the same as yours, they may have the same problem, but it wont be caused by anything spreading from your house
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    best way to mix small amounts of mortar?

    Pre mixed bagged mortar and concretes are ideal for these applications, some are even available in tubs. Postcrete is definitely the best solution to fixing fence posts
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    crumbly concrete under floor

    Only absolute way to tell if it's sulphate attack is to get some of the concrete tested (measure sulphate content and get it looked at under a microscope)- Try Sandbergs ! If it is sulphate attack, the concrete needs to removed , a dpm put in place and new concrete put in. If you use...
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    How to remove salt from cement render?

    Repeated brushing is the best way, but you also try a weak acid based brickwork cleaner when you are brushing. But as PVMS said, dont get it too wet. The white deposits are soluble salts which are drawn to the surface and dry out. If you saturate the bricks, all you do is provide more salts and...
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    Sand and Cement

    Hi Fair enough, Portland cement (CEM I) and Portland-fly ash cement (CEM II/B-V) are usually OK but be careful with the cements that already contain air (sometimes called 'enhanced' cements), such as Lafarge Mastercrete Hope this helps
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    Sand and Cement

    Make sure you check what type of cement you have bought, not all of them are comptible with Freeflo (see the back of the Freeflo tub)
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